"extensive delays" is correct and usable in written English.
You can use this phrase to describe a situation in which something takes longer than expected or anticipated. For example, "The construction project ran into extensive delays due to the extreme weather conditions."
"Customers often never know that they have avoided extensive delays".
Those reports have brought whole subway lines to a halt during the rush hours, causing extensive delays.
Motorists were urged to find alternative routes with extensive delays on all approaches to the busy arterial road.
On the AirTrain from Jamaica station to Kennedy, traveler after traveler told stories of flight cancellations and extensive delays.
An internal electrical problem caused extensive delays on several subway lines on the East Side of Manhattan yesterday, Transit Authority officials said.
Some travelers say that when they initially complained about extensive delays or other poor service, they were first offered gift certificates that fell short of the ticket price.
The committee's report lambasts the project's "extensive delay", not to mention "the waste of a yet to be determined amount of public money".
Such an extensive delay is rare in the Alexandria courthouse, which is known as the "rocket docket" because of the insistence of its judges that cases be brought to trial quickly.
The session was subject to an extensive delay because of problems with the weather and the medical helicopter.
Committee chairman Margaret Hodge said: "The failure to develop a comprehensive plan has led to extensive delay and the waste of a yet to be determined amount of public money.
It will also provide lodging if I'm delayed more than four hours overnight, and food and drink vouchers "in the event of an extensive delay".
